This invention relates to a supported gas separation membrane for separating a particular gaseous component from a mixture of gases. More particularly, this invention is directed to a gas separation membrane having an asymmetric gas separation membrane layer and a porous polymeric support layer, to a process for its manufacture and to a process for its use in separating a particular component from a mixture of gases.
The use of a gas separation membrane for separating a particular component from a mixture of gases is well known. See, e.g., U.S. Pat. Nos. 4,512,893, 4,717,394, 4,818,452, 4,902,422, 4,981,497, 5,042,993, 5,067,970, 5,165,963, 5,178,940, 5,234,471, 5,248,319, 5,262,056, 5,633,039 and 5,591,250. Examples of the type of gases separated by a gas separation membrane include carbon dioxide from methane, hydrogen from various gas mixtures, organic vapors from various gas mixtures, producing nitrogen, producing oxygen enriched air, etc. When using a gas separation membrane to separate a particular component from a gas mixture, one side of the membrane will be contacted with a complex multicomponent gas mixture. Typically, certain gas(es) in the gas mixture will permeate through the gas separation membrane at a faster rate than the other gas(es). The gas permeation rate through the gas separation membrane is a property of the membrane material composition and its morphology.
Gas separation membranes may be asymmetric, i.e., possessing a relatively dense, nonporous region and a relatively less dense, porous region, or they may be symmetric, i.e., possessing a substantially uniform, nonporous structure throughout. Examples of an asymmetric gas separation membrane can be found in U.S. Pat. Nos. 4,512,893, 4,818,452, 4,902,422, 5,067,970, 5,165,963, 5,178,940 and 5,633,039. This type of gas separation membrane can be obtained by a solvent evaporation/coagulation procedure.
U.S. Pat. No. 5,591,250 discloses an unsupported, symmetric gas separation membrane derived from a certain class of polyimides.